<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../jquery-3.3.1.min.js"></script>
    <style>
        .oo {
            background-color: black;
        }
    </style>
</head>

<body>
    <button id="close">关灯</button>
    <button id="open">开灯</button>
    <script>
        $("#close").click(function() {
            $("body").css("background-color", "black");
        });
        $("#open").click(function() {
            $("body").css("background-color", "white");
        });
    </script>
</body>

</html>